IMPLICATIONS OF CHANGING AID PROGRAMS TO U.S. AGRICULTURE

Agricultural Finance,

Threats to soil quality in Denmark - A review of existing knowledge in the context of the EU Soil Thematic Strategy

The EU Commission is preparing a proposal for a Soil Framework Directive with the purpose of protecting the soil resources in Europe. The proposal identifies six major threats to the sustained quality of soils in Europe. This report addresses the threats that are considered most important under the prevailing soil and climatic conditions in Denmark: compaction, soil organic matter decline, and erosion by water and tillage. For each of these threats, the relevance and damage to soil functions as well as the geographic distribution in Denmark are outlined. We suggest a procedure for identifying areas at risk. This exercise involves an explicit identification of: i) the disturbing agent (climate / management) exerting the pressures on soil, and ii) the vulnerability of the soil to those stresses. Risk reduction targets, measures required to reach these targets, and the knowledge gaps and research needs to effectively cope with each threat are discussed. Our evaluation of the threats is based on soil resilience to the imposed stresses. Subsoil compaction is considered a severe threat to Danish soils due to frequent traffic with heavy machinery in modern agriculture and forestry. The soil content of organic matter is critically low for a range of Danish soils, which should be counteracted by appropriate management options. Soil erosion by tillage, and to a lesser degree by water, adversely affects soil quality on much of the farmland because degradation rates are much higher than generation of soil

Soil Quality Management - Concepts and Terms

The industrialization of agriculture and the concurrent increase in societal concerns on environmental protection and food quality have put focus on agricultural management and its impact on soil quality. Soil quality involves the ability of the soil to maintain an appropriate productivity, while simultaneously reducing the effect on the environment and contributing to human health. This development has changed society’s expectations to science and there is an urgent need to improve the communication among researchers from different scientific disciplines. The interaction of scientists with decision-makers is a topic of utmost relevance for future developments in agriculture. Reflexive objectivity denotes the exercise of raising one’s consciousness of the cognitive context, i.e. societal priorities and the values and goals of the researcher. The term sustainability comprehends the priorities in the cognitive context and thus constitutes a valuable tool for expressing the basis of scientific work. Soil quality evaluations should include awareness of the stability of any given quality attribute to disturbance and stress. This implies addressing resistance and resilience of the soil functions and/or the physical form in question. Most existing literature on soil quality focuses on assessment of soil quality rather than the management tools available to influence soil quality. Identification of management thresholds rather than soil quality indicator thresholds is suggested as an important means of implementing the soil quality concept. The major challenges facing modern agriculture include proper nutrient cycling, maintained functions and diversity of soil, protection of an appropriate physical form, and avoidance of chemical contamination. It is suggested that these challenges and problems as related to the soil quality concept are discussed in the framework expounded above

Oedipus of many pains: Strategies of contest in Homeric poetry

In this paper we analyse Oedipus’ appearance during Odysseus’ tale in book 11 of Homer’s Odyssey in order to outline and test a methodology for appreciating the poetic and thematic implications of moments when ‘extraneous’ narratives or traditions appear in the Homeric poems. Our analysis, which draws on oral-formulaic theory, is offered partly as a re-evaluation of standard scholarly approaches that tend to over-rely on the assumed pre-eminence of Homeric narratives over other traditions in their original contexts or approaches that reduce such moments to instances of allusions to or parallels with fixed texts. In conjunction with perspectives grounded in orality, we emphasise the agonistic character of Greek poetry to explore the ways in which Odysseus’ articulation of his Oedipus narrative exemplifies an attempt to appropriate and manipulate a rival tradition in the service of a particular narrative’s ends. We focus specifically on the resonance of the phrases algea polla and mega ergon used by Odysseus as a narrator to draw a web of interconnections throughout Homeric and Archaic Greek poetry. Such an approach, in turn, suggests to what extent the Homeric Oedipus passage speaks to the themes and concerns of Homeric poetry rather than some lost Oedipal epic tradition and illustrates the importance of recognizing the deeply competitive nature of Homeric narratives vis-à-vis other narrative traditions

Verifying the mass-metallicity relation in damped Lyman-alpha selected galaxies at 0.1<z<3.2

A scaling relation has recently been suggested to combine the galaxy mass-metallicity (MZ) relation with metallicities of damped Lyman-alpha systems (DLAs) in quasar spectra. Based on this relation the stellar masses of the absorbing galaxies can be predicted. We test this prediction by measuring the stellar masses of 12 galaxies in confirmed DLA absorber - galaxy pairs in the redshift range 0.1<z<3.2. We find an excellent agreement between the predicted and measured stellar masses over three orders of magnitude, and we determine the average offset $\langle C_{[M/H]} \rangle$ = 0.44+/-0.10 between absorption and emission metallicities. We further test if $C_{[M/H]}$ could depend on the impact parameter and find a correlation at the 5.5sigma level. The impact parameter dependence of the metallicity corresponds to an average metallicity difference of -0.022+/-0.004 dex/kpc. By including this metallicity vs. impact parameter correlation in the prescription instead of $C_{[M/H]}$, the scatter reduces to 0.39 dex in log M*. We provide a prescription how to calculate the stellar mass (M*,DLA) of the galaxy when both the DLA metallicity and DLA galaxy impact parameter is known. We demonstrate that DLA galaxies follow the MZ relation for luminosity-selected galaxies at z=0.7 and z=2.2 when we include a correction for the correlation between impact parameter and metallicity.Comment: 15 pages, 6 figures. Major revision. Accepted for publication in MNRA

Transitions in non-conserving models of Self-Organized Criticality

We investigate a random--neighbours version of the two dimensional non-conserving earthquake model of Olami, Feder and Christensen [Phys. Rev. Lett. {\bf 68}, 1244 (1992)]. We show both analytically and numerically that criticality can be expected even in the presence of dissipation. As the critical level of conservation, $\alpha_c$, is approached, the cut--off of the avalanche size distribution scales as $\xi\sim(\alpha_c-\alpha)^{-3/2}$. The transition from non-SOC to SOC behaviour is controlled by the average branching ratio $\sigma$ of an avalanche, which can thus be regarded as an order parameter of the system. The relevance of the results are discussed in connection to the nearest-neighbours OFC model (in particular we analyse the relevance of synchronization in the latter).Comment: 8 pages in latex format; 5 figures available upon reques

Searching the critical soil organic carbon threshold for satisfactory tilth conditions – test of the Dexter clay:carbon hypothesis

The concern for deteriorating soil structure at low soil organic matter (SOM) contents calls for better knowledge of SOM interaction with soil minerals as well as guidelines for soil conservation. We measured clay dispersibility in a field with a textural gradient. Our results support the concept of differentiating soil content of clay in a complexed and non-complexed part although our data did not point out an exact clay/OC ratio threshold. Our results also indicated that labile fractions of SOM may play an important role in soil physical behavior. We revisited literature data and found evidence that soil content of fines (<2 or <20 μm) is a major determinant of soil specific surface area (SA). We noted that soil SA coverage with SOM changed dramatically at a specific ratio of either clay (<2 μm) or clay+silt (<20 μm) with soil OC. This is an indirect support of the recently suggested quantification of the soil mineral ‘saturation’ hypothesis. More studies are needed on the causal relationships. We conclude that clay/OC~10 or (clay+silt20μm)/OC~20 are corresponding indices reflecting shift in soil physical behavior